Electronic devices such as electronic book reader devices (“eBook reader devices”), cellular telephones, portable media players, desktop computers, laptops, tablet computers, netbooks, personal digital assistants, and the like, rely on electrical power to function.
Within these electronic devices, several components utilize power during operation, including the processor(s) and peripheral devices. These peripherals include external memory interfaces (EMIs), Universal Serial Bus (USB) host controllers, USB device controllers, image processing units (IPUs), and so forth. These peripherals may reside on the same “chip” or die as the processor, on another die, or a combination of same die and another die.
An idle device controller, such as on a USB interface, consumes power. This wastes energy and increases the amount of heat dissipated by the electronic device. Reducing power consumption increases the usable time for a portable device operating from a battery. Reducing power consumption also reduces the heat dissipated by the electronic device, allowing it to operate at a cooler temperature and thus increasing the life of the equipment and simplifying the cooling design.
Various schemes have been put forth to reduce power consumption in portable consumer devices by placing the processor of the device and certain peripherals into lower power modes. However, traditionally these schemes focus on reducing the power consumed by processors, memory, and so forth.